The present invention relates to a packaging material of the type in which a storage case storing data recording cartridges are stored is put in an outer case for protection, and a packaging structure for packaging the storage case using this packaging material.
Traditionally, cartridges for recording media such as disc cartridges and tape cartridges (also simply referred to as cartridges) may be replaced collectively in large numbers for backup of a host computer and the like. In such a case, a packaging type in which cartridges are each separately stored in cases is troublesome in handling. Therefore, considering working efficiency, for example, a bulk specification packaging type in which a plurality of, for example, about twenty cartridges, are collectively stored in one plastic storage case is preferred.
However, with the bulk specification packaging type, the plastic storage cases are directly inserted in an outer case (a corrugated cardboard case). Since the outer case contains a large number of cartridges and relatively has a large mass, when the outer case containing the storage case is erroneously dropped due to handling during shipping and the like, the storage case may be damaged. In particular, when an outer case 20 is dropped so that its ridge portion falls off to a floor F first as shown in FIG. 9, a large load is applied to a corner portion of a bottom surface of the storage case. Therefore, as shown in FIG. 10, a ridge portion of a storage case 40 is continuously damaged in a straight line, so that a cartridge may be deformed. It is the lower-side ridge portion that is damaged. However, for the sake of convenience, FIG. 10 shows the storage case 40 with its upper and lower sides flipped in order to clearly show a damaged state of the storage case 40.
Further, in particular, in the case where the recording media are tapes, and the tapes are arranged so that their slots (access slots) face the direction of the dropped ridge portion, since a tape slot is structurally low in strength, a cartridge is easily damaged. The reason therefor is considered as follows: The storage case moves greatly inside the outer case at the time of the dropping, and a corner portion of the storage case is subjected to a strong impact from the floor. If the slot of the tape is damaged, the position of a leader pin that is a tape leading member provided therein is displaced, and there is fear that a chucking error may occur when the cartridge is inserted into a drive.
In response to this, Patent Document 1 discloses a packaging structure for restricting movement of a storage case 40 inside an outer case 20.
The packaging type of Patent Document 1 is shown in FIGS. 11 and 12. As shown in the figures, Patent Document 1 discloses the configuration in which when the storage case 40 is put in the outer case 20, the storage case 40 is positioned to the outer case 20. Specifically, openings are formed in flaps 23 of the outer case 20 corresponding to projecting portions 48a formed on an upper surface 47a of the storage case 40. The storage case 40 is put in the outer case 20 and the flaps 23 are closed, whereby the openings 25 of the flaps are engaged with the projecting portions 48a. 
The storage case 40 consists of an upper case 41 and a lower case 42 that are joined at flanges respectively projecting outward from their sides. The projecting portions 48a are also formed on a lower surface of the lower case 42 in addition to those formed on the upper surface of the upper case 41. They are formed of fitting ribs, each having a rectangular-shaped annular shape, so that, when a plurality of the storage cases 40 are stacked, they are fitted to each other.
Patent Document 1: JP2009-286425 A
If the packaging type of Patent Document 1 is adopted, the storage case 40 hardly moves inside the outer case 20, however, it is difficult to obtain a sufficient buffer effect. The reason therefor is as follows: As shown in FIG. 12, the flaps 23 are slanted when the outer case 20 is closed due to the structure of the flaps 23 of the outer case 20. Therefore, an opening 25 and a projecting portion 48a are relatively deeply engaged with each other in the vicinity of an end of a folded flap 23, however, an engaged state between the opening 25 and the projecting portion 48a becomes shallow in the vicinity of a basal portion of the flap 23.
The present invention was made in view of the problem described above. An object thereof is to improve the buffer effect on cartridges as well as to make it possible to suppress deformation or breakage of the cartridges in the case where, after a storage case containing data recording cartridges has been put in an outer case for packaging, the outer case is dropped.